1. Field of the Invention
The present invention relates to a magnetic recording medium having a super thin film coating type magnetic layer. More particularly, it relates to a coating type magnetic recording medium adaptable to an MR (magnetic resistance) head.
2. Description of the Related Art
A magnetic recording system composed of a combination of an MR head and a coating type magnetic recording medium has come under review with a tendency toward higher density of a magnetic recording medium. For example, Japanese Patent Laid-Open Publication No.Hei 10-312525 discloses that by implementing a hexagonal ferrite powder-containing magnetic layer with a saturation magnetic flux density of from 300 to 1000 G, and a coercive force of 2000 Oe or more, or a ferromagnetic metal powder-containing magnetic layer with a saturation magnetic flux density of from 800 to 1500 G, and a coercive force of 2000 Oe or more, a magnetic recording medium excellent in cost efficiency, and ensuring a low noise and excellent in high density characteristics can be obtained. Further, Japanese Patent Laid-Open Publication No.Hei 10-302243 discloses that, by regulating the protrusion height on the magnetic layer surface and the magnetization reversal volume and by making a coercive force be 2000 Oe or more, a magnetic recording medium suitable for reproduction by an MR head and with improved durability and noise can be implemented.
On the other hand, for a method for coating a high density recording medium in recent years, Japanese Patent Publication No.Hei 05-059490 discloses a method in which a non-magnetic coating material is applied on a non-magnetic substrate, and a magnetic layer with a thickness of 1 μm or less is applied thereon while the non-magnetic coating material is still in a wet state.
However, the foregoing prior art methods are still insufficient for obtaining a low noise medium suitable for an MR head. For example, with the method in which a non-magnetic coating material is applied on a non-magnetic substrate, and a magnetic layer with a thickness of 1 μm or less is applied thereon while the non-magnetic coating material is still in a wet state as described in Japanese Patent Publication No.Hei 05-059490, the surface properties of the non-magnetic substrate directly affect the magnetic layer to cause noise degradation. Further, in actuality, a detailed description is not given to the relationship between the magnetic powder used and a noise in the prior art.